Nginx is open source software for web serving, reverse proxying, caching, load balancing, media streaming, and more. It started out as a web server designed for maximum performance and stability. In addition to its HTTP server capabilities, Nginx can also function as a proxy server for email (IMAP, POP3, and SMTP) and a reverse proxy and load balancer for HTTP, TCP, and UDP servers.
An Apache web server can host multiple websites on the SAME server. You do not need separate server machine and Apache for each website. This can be achieved using the concept of Virtual Host or VHost.
Any domain that you want to host on your web server will have a separate entry in Apache configuration file.
Apache or Apache HTTP server is a free and open source web server, developed and maintained by the Apache Software Foundation. It is one of the most popular web servers in the world. Apache allows website developers to serve their content over the web and provides many powerful features that can be extended through additional modules.